Printer wiper for printing on bichromal or multi-colored electronic paper

ABSTRACT

An electronic display includes an electronic display material having two opposing outer surfaces, wherein at least one of the outer surfaces is at least partially covered in a plurality of spaced-apart charge-retaining islands comprised of a conductive material with areas of insulating material interposed therebetween. A charge transfer device is arranged in operative association with the display material, and includes a first component made of a pliable, nonconductive material and at least one conductive portion, and a second component configured to support the first component. Alternatively, a charge transfer device is configured to transfer an electric charge to charge-retaining islands of an electric display, where the charge-retaining islands are on a surface of the electric display and are spaced apart with areas of insulating material interspersed therebetween. The charge transfer device includes a first component made of a pliable nonconductive material and at least one conductive portion, and a second component made of a material to support the first component.

This is a continuation of application of U.S. Ser. No. 10/739,613, filedDec. 18, 2003, entitled “Printer Wiper For Printing On Bichromal OrMulti-Colored Electronic Paper”, by Gregory P. Schmitz, the disclosureof which is hereby incorporated by reference in its entirety.

BACKGROUND

This application relates to the use of electronic display systems, andmore particularly to components used in the generation of images on thedisplays. In one embodiment the display systems are designed to includegyricon electric reusable paper but may also be electric reusable paperbased on liquid crystal, electrophoretic, and other field-effect displaytechnologies.

Electric reusable paper can be defined as any electronically-addressabledisplay medium that approximates paper in form and function. Electricreusable paper should be light-weight, thin, and flexible, and it shoulddisplay images indefinitely while consuming little or no power. Inaddition, electric reusable paper should be re-usable. One must be ableto erase images and create new ones repeatedly. Preferably, electricreusable paper should display images using reflected light and allow avery wide-viewing angle.

One way to make electric reusable paper possible using traditionalelectronic display technology is to completely remove the drivingelectronics from an electronic display package and use externaladdressing electrodes to write and erase images. This approach bothreduces the per unit cost of electronic paper sheets and enables the useof cheap, flexible plastic films in place of glass plates for packaging.Multiple electronic paper sheets can then be addressed by a single setof external driving electronics, much like multiple sheets of pulp paperare printed on by a single printer.

A sheet and display system dubbed gyricon is disclosed in variouspatents and articles, such as U.S. Pat. No. 4,126,854 by Sheridon,titled “Twisting Ball Display”, incorporated herein in its entirety. Thegyricon display system is comprised of a host layer a few mils thickwhich is heavily loaded with bichromal elements, possibly spheres,several microns in diameter. In one implementation, each bichromalelement has halves of contrasting colors, such as a white half and ablack half. Each bichromal element also possesses an electric dipole,orthogonal to the plane that divides the two colored halves. Eachbichromal element is contained in a cavity filled with a dielectricliquid. Upon application of an electric field between electrodes locatedon opposite surfaces of the host layer, the bichromal elements willrotate depending on the polarity of the field, presenting one or theother colored half to an observer. It is noted that in addition to blackand white electric displays, electric displays providing highlight colorand additive full color have been disclosed. U.S. Pat. No. 6,456,272 byHoward et al., titled, “Field Addressed Displays Using ChargeDischarging in Conjunction With Charge Retaining Island Structures”, andU.S. Pat. No. 5,717,515 by Sheridon issued Feb. 10, 1998 and titled“Canted Electric Fields For Addressing A Twisting Ball Display” (eachincorporated by reference in their entirety herein) describe severalmethods for making highlight color and full color versions of a electricreusable paper substrate and display.

An electric reusable paper substrate has many of the requisitecharacteristics of electric reusable paper, namely, bistable imageretention, wide viewing angle, thin and flexible packaging, and highreflectance and resolution. U.S. Pat. No. 5,389,945 issued to Sheridonon Feb. 14, 1995, and titled “Writing System Including Paper-LikeDigitally Addressed Media And Addressing Device Therefor”, incorporatedin its entirety herein by reference, describes an electric reusablepaper printing system that employs independent, external addressingmeans to put images on the Electric reusable paper substrates. Theexternal addressing means is described as a one-dimensional array ofelectrodes connected, either directly or by wireless technology, tomodulating electronics. As the one-dimensional array is scanned acrossthe sheet, modulating electronics adjust the potential at the individualelectrodes, creating electric fields between the electrodes and anequipotential surface. An image is created in the sheet according to thepolarity of the electric fields.

A common implementation of electric displays will use charge-retainingisland patterning on the electric reusable paper sheets. This techniquehas been described in U.S. Pat. No. 6,222,513 by Howard et al., titled“Charge Retention Islands For Electric Paper And Applications Thereof”,incorporated in its entirety herein by reference.

Charge-retaining island patterning is an electric reusable paper sheetthat uses a pattern of conductive charge-retaining islands on theoutward-facing side of at least one of two opposed outward surfaces. Thesecond outward surface may also be coated with a conductive material, ormade of a conductive material, and may or may not be patterned. Thecharge-retaining islands of the patterned surface or surfaces receiveelectric charges from an external charge-transfer device. After thecharge-transfer device is removed, the conductive, charge-retainingislands hold electric charge, creating an electric field in the electricreusable paper of sufficient magnitude and duration to cause an imagechange.

An alternate embodiment of the charge-retaining island approach utilizescharge-retaining islands which are created as part of the bulk of theencapsulating layer instead of being patterned on the surface of thelayer. Extending the conductivity of the charge-retaining islandsthrough the bulk of the encapsulating layer to the sheet containedtherein improves the performance of the charge-retaining islands andreduces problems of image instability when handled immediately afteraddressing.

A suitable mechanism for transferring charge to charge-retaining islandsis by contact charging, whereby, a mechanical contact is made betweenconductive contact elements of an external charge transfer device andthe conductive charge-retaining islands. When in contact, charge istransferred across the interface bringing the charge-retaining islandsto the same electric potential as the contact elements. Charge remainson the charge-retaining islands, maintaining a voltage and an electricfield in the sheet, well after contact is broken and the contactelements are removed from the writing area.

Mechanical contact may be made by use of a charge transfer deviceconfigured with alternating conductive charge transferelements/conductors and insulating material. For proper operation, thecharge transfer conductors need to make reliable contact to thecharge-retaining islands while moving with respect to the electric papersheet during image generation. Arrays using springy wire electrodessoldered to the edge of a printed circuit board have been demonstrated.More robust arrays utilizing anisotropically conductive elastomerconnectors, such as Zebra connectors (e.g., conductive strip), as knownin the art, have also been used.

A practical concern of proposed systems for printing on electric paperis the inability to insure reliable contact between the charge transferdevice and the charge-retaining islands. The conductive strip andflexible printed circuit board strip commonly used to charge acharge-retaining island on electric paper, exhibit no appreciable memory(i.e., rigidity) along their length or width, making contact with thecharge-retaining islands inconsistent, and thereby limiting printquality.

This inconsistent contact is exacerbated due to the non-planar surfacesof the electric paper. Particularly, existing manufacturing processesfor forming the surface of electric paper cause imperfections andoscillations in its surface and, therefore, an undulating profile forthe surface carries the charge-retention islands. Additionally, thesurface may further have to deal with dirt and/or debris located in theinsulating channels between the charge-retention islands. Due to thesupple nature of the charge transfer device, when the charge transferdevice operate in such environments, direct contact between theconductive strip and the electric paper surface is not fully maintained.Therefore, charging of the charge-retaining islands is inconsistent,resulting in streaks and fringes on the printed image.

SUMMARY

An electronic display includes an electronic display material having twoopposing outer surfaces, wherein at least one of the outer surfaces isat least partially covered in a plurality of spaced-apartcharge-retaining islands comprised of a conductive material with areasof insulating material interposed therebetween. A charge transfer deviceis arranged in operative association with the display material, andincludes a first component made of a pliable, nonconductive material andat least one conductive portion, and a second component configured tosupport the first component.

Alternatively, a charge transfer device is configured to transfer anelectric charge to charge-retaining islands of an electric display,where the charge-retaining islands are on a surface of the electricdisplay and are spaced apart with areas of insulating materialinterspersed therebetween. The charge transfer device includes a firstcomponent made of a pliable nonconductive material and at least oneconductive portion, and a second component made of a material to supportthe first component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an electric reusable paper sheet,according to the present application;

FIG. 2 shows an enlarged cross-sectional view of an electric reusablepaper sheet according to the present application;

FIG. 3 is an electric reusable paper sheet illustrating a Zebraconductive wand implementation;

FIG. 4 depicts a non-planar surface which results in a non-reliablecontact between the charge transfer device and the charge-retentionislands;

FIG. 5 shows an illustrated view of a first embodiment of a wand-typestructure in accordance with the concepts of the present application;

FIG. 6 is a side view of FIG. 5 with additional structure for holdingthe wand design;

FIG. 7 illustrates a second embodiment for the present application;

FIG. 8 is a side view of FIG. 7 with additional structure to hold thewand implementation of the present embodiment;

FIG. 9 is a third embodiment of a wand in accordance with the presentapplication;

FIG. 10 is a side view of FIG. 9, including additional structure forholding the wand design;

FIG. 11 depicts a further embodiment and a testing element for testingthe pressure delivered by the wand design;

FIG. 12 is a side view of FIG. 11 with additional structure showingattachment of the wand design and a testing configuration fordetermining the pressure applied to the charge-retention islands; and

FIG. 13 illustrates that each of the embodiments described may beimplemented in a bidirectional system where the additional supportstructure is located on both sides of the conductive strip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to FIG. 1 an electric reusable paper sheet, according to anembodiment described in the present application, is shown. The electricreusable paper sheet includes an electric reusable paper substrate suchas a gyricon sheet 10 which contains bichromal elements 20, a firstencapsulating layer 12 patterned with conductive charge-retainingislands 14, and a second encapsulating layer 16 that may or may not bepatterned with charge-retaining islands. Although the bichromal elements20 are pictured here as substantially spherical, it should be noted thatother configurations are also possible. In particular, bichromalelements that are substantially cylindrically shaped are also known. Acomplete discussion of twisting cylinder electric reusable papersubstrates, their use and manufacture can be found in U.S. Pat. No.5,894,367 issued Apr. 13, 1999, titled “Twisting Cylinder Display UsingMultiple Chromatic Values” by Sheridon, incorporated by reference hereinin its entirety.

Together, the first encapsulating layer 12 and the second encapsulatinglayer 16 is configured to do the following things: contain an electricreusable paper substrate 10, provide at least one transparent windowthrough which the electric reusable paper substrate 10 can be viewed,and provide at least one external surface patterned withcharge-retaining islands 14 that can be addressed with an externalcharge transfer device. The first encapsulating layer 12 and secondencapsulating layer 16 could take the form of thin plastic sheets thatare sealed or fastened around the perimeter of the electric reusablepaper substrate 10. The second encapsulating layer 16 need not beentirely separate from the first encapsulating layer 12. The secondencapsulating layer 16 could simply be an extension of the firstencapsulating layer 12, folded over and around the edge of the sheet andthen sealed or fastened around the remaining perimeter. The firstencapsulating layer 12 and second encapsulating layer 16 could also takethe form of a coating, applied by spraying, doctoring, or some othermethod to hold the contents of the electric reusable paper substrate 10.

Charge-retaining islands 14 have square perimeters and are organized ina simple two-dimensional x-y matrix. Narrow channels 18 of encapsulatingmaterial layer 12 separate the charge-retaining islands 14. The channels18 serve to isolate the charge-retaining islands 14, preventingmigration of charge laterally across the encapsulating sheet, and shouldbe small with respect to the charge-retaining islands 14, so that themaximum possible area of the display is covered with conductivecharge-retaining material. The channels 18 must not become so small,though, that they fail to prevent significant charge leakage across thecharge-retaining islands 14. Even if island-channel proportions areproperly designed, in practice, dirt and accumulated debris can provideconduction paths across channels. Therefore, it is important to keep thesurface of the patterned encapsulating layers clean.

It should be noted that the charge-retention islands need not beimplemented in a regular two-dimensional pattern utilizing an x-ymatrix. Other patterns are possible including a charge-retaining islandpattern that utilizes a random array. When using other patterns, it isimportant that the charge-retaining islands 14 be relatively largecompared to the channels 18. In a random distribution, both featuresizes must be much smaller than the pixel size of a displayed image.Pixel size is determined by the size or range of addressing elements ofan external charge transfer device independently of the size of thecharge-retaining islands 14. The charging array need not be registeredor aligned perfectly with the pattern, though, because large groups ofislands are charged by each addressing element and moire effects arenegated by the randomness of the island pattern.

The electric reusable paper substrate 10 can be constructed bytechniques already known in the art. The charge-retaining islands 14 canbe created on or in the encapsulating layer 12 by many means with anysuitably conductive material. One technique creates islands ofconductive and transparent Indium Tin Oxide (ITO) on a z-axis onlyconductive film. Z-axis conductive films are known and generally consistof a matrix loaded with conductive particles, such as silver coatedglass beads, to allow for an electrically conductive interconnectionthrough the films thickness. However, the conductive particles arespaced far enough apart to be electrically insulative in the plane ofthe film. The z-axis only conductive film is coated with a very thinlayer of ITO, and then channels are etched in the ITO byphotolithographic processes well known in the art. The remainingconductive ITO regions act as charge-retaining islands, while thechannels 18 are created by the underlying z-axis only conductive film.Any conductive material such as chrome, aluminum, polyaniline which canbe applied to form discontinuous conductive regions could be used inplace of the ITO. Many z-axis only conductive materials, such as thosemade by 3M Corporation of St. Paul, Minn., Fuji Poly of Kenilworth,N.J., or Shin-Etsu Polymer Company, Limited of Japan, are possiblecandidates for a substrate on which to build the islands.

FIG. 2 shows an enlarged cross-sectional view of the electric reusablepaper sheet shown in FIG. 1 taken through cross-section line 2--2. Ascan be seen in FIG. 2, the encapsulating layer 12 is clearly comprisedof alternating conductive regions 22 and non-conductive regions 24. Therotational element 20, the charge-retaining island 14, and theconductive regions 22 each have a size s1, s2, and s3 respectively. Thesize s2 of the charge-retaining island 14 is shown to be on the order ofthe same magnitude of the size s1 of the rotational element 20. Toachieve element rotation the size s2 of the charge-retaining island 14should be no smaller than ½ the size s1 of the rotational element 20.The size of the conductive region s3 however, is substantially smallerthan the size s2 of the charge-retaining island 14. The size of theconductive regions 22 should be kept as small as possible, but no largerthan ⅓ of the size of the charge-retaining island 14. The conductiveregions 22 in the encapsulating layer need not be of uniform size ordistribution throughout the encapsulating layer 12, however they shouldbe small enough and distributed enough throughout the encapsulatinglayer 14 such that at least one conductive region 22 is associated withas many charge-retaining islands 14 as possible for optimal performance.

Also, the conductive regions 22 should be placed relative to thecharge-retaining islands 14 so that they do not bridge the channel 18between two charge- retaining islands 14. The size and distribution willvary with manufacturing techniques. For instance, if accurate placementof the conductive regions 22 can not be maintained then it may bedesirable to make the conductive regions 22 much smaller than the sizeof the channel 18 to insure that a conductive region 22 can not bridgethe channel 18 between two charge-retaining islands 14 as shown in FIG.2.

The size s3 of any single conductive region 22 is too small toeffectively rotate the rotational element. However, the charge-retainingisland 14 in conjunction with the conductive regions 22 can togethereffectively be addressed and achieve rotation of the rotational elementwithout suffering from the image instability problems associated withcharge removal when an electric reusable paper sheet is handledimmediately after addressing.

An external charge transfer device must also be chosen to work with acharge-retaining island pattern. Examples are described in U.S. Pat. No.6,222,513 by Howard et al., titled “Charge Retention Islands ForElectric Paper And Applications Thereof”, and U.S. Pat. No. 6,456,272 byHoward et al., titled “Field Addressed Displays Using Charge DischargingIn Conjunction With Charge Retaining Island Structures”, bothincorporated by reference herein above. As mentioned, a suitablemechanism identified for transferring charge to charge-retainingislands, is contact charging, whereby, a mechanical contact is madebetween conductive contact elements of an external addressing array andthe conductive charge-retaining islands. When in contact, charge istransferred across the interface bringing the charge-retaining islandsto the same electric potential as the contact elements. Charge remainson the charge-retaining islands, maintaining a voltage and an electricfield in the sheet, well after contact is broken and the contactelements are removed from the writing area.

Various mechanical arrangements have been envisioned for external chargetransfer devices that utilize the above charge transfer mechanisms. Oneof these is a one-dimensional array of charge transfer elements whichcould be built and used like a print head or wand. The contact chargingwand is comprised of alternating conductive charge transfer elements andinsulating elements.

The charge-retaining islands technique, described above, can also beused to implement a gyricon with grey scales, highlight color, additivefull color, or custom colors using only simple bichromal elements.

FIG. 3 shows a portion of a electric reusable paper sheet 30 with anarrayed charge transfer device 32 configured as a conductive strip orwand (i.e., Zebra conductor), which in one embodiment is made of anelastomer, plastic or other flexible, compliant non-conductive material34, with conductive wires 36 embedded or otherwise connected toconductive material 34. The electric reusable paper sheet 30 comprisesan electric reusable paper substrate, such as gyricon sheet 38 withfluid filled cavities 40, wherein each cavity contains a bichromalelement such as bichromal element 42 which is divided into two differentportions 44, 46, each portion having an optical characteristic. Onesurface of the electric reusable paper sheet 30 is covered with aconductive material 48 to provide an equipotential surface while theother surface of the electric reusable paper sheet 30 is covered with anarray of charge-retaining islands 50 separated by channels 52. It shouldbe noted that this particular configuration is used for illustrativepurposes only and the foregoing described variations in charge transferdevices and construction of charge-retaining islands and equipotentialsurfaces are also applicable. Further, while FIG. 3 shows only onebichromal element associated with each charge- retaining island inpractice it would be more likely that many bichromal elements would beassociated with a given charge-retaining island. In such instances, thebichromal elements can be arranged in any pattern such as close packedarray or a random distribution as is already known in the art.Furthermore, while the bichromal elements are shown as bichromal spheresin this drawing, they need not be spheres but might also be bichromalcylinders as described in U.S. Pat. No. 6,055,091, titled “TwistingCylinder Display”, by Sheridon et al., assigned to the same assignee andherein incorporated by reference in its entirety.

Turning to FIG. 4, illustrated is a side view of electric usable papersheet 30 with conductive strip (i.e., Zebra conductor) 32, shown atstages a-f as conductive strip 32 moves over the surface comprised ofislands 50 and channels 52. One difference between this implementationand that of FIG. 3, is that in at least one of the channels 52, animpediment 64, such as a deformation of the surface occurring duringmanufacture, or dirt/debris on the surface causes the surface to beother than planar. As previously noted, and as illustrated in themovement of charge transfer device 32 through steps a-f, such impedimentmay cause incomplete contact between charge transfer device 32 and thesurface of charge-retaining islands 50. More specifically, as shown atpoint a, movement of charge transfer device 32 starts below islandsurface 50, whereby the entire surface of charge-retaining island 50will come into contact with conductive wires 36, a charge transferdevice 32 is moved along, as shown at position b. However, at positionc, the charge transfer device 32 impinges on impediment 64. A it passesthe impediment and reaches position d, conductive wire 36 is not incontact with the surface of charge-retaining island 50. In some cases,there will be time for charge transfer device 32 to have contact withsome portion of the island as shown at point e. However, in otherinstances, there will be no contact until movement is to the nextcharge-retaining island 50.

Also, while charge transfer device 32 is shown touching the surface ofcharge-retaining island 50 in step e, even if there is contact, thecontact may be insufficient to permit a proper transfer of charge.

As also illustrated in FIG. 4, it is desirable to have a sharp edge ofconductive strip 32 to come into contact with the charge-retainingislands 50. Another drawback of an overly flexible conductive strip isillustrated at position f. In this instance, when the downward pressureis over a certain value, the compression in the conductive strip willcause the sharp end to curl up in an undesirable fashion. Thus, withinsufficient support, this curled-up position results in aless-than-desirable contact between the conductive strip andcharge-retaining islands.

In one implementation, the charge transfer device 32, when formed as aconductive strip is in a range of approximately 0.01 and 0.04 inchesthick, and is preferably 0.02 inches thick. It is supple and without anyappreciable resistance to flexior along its length and width. Theconductive strip can be visualized as a windshield wiper on anautomobile being swiped across the gyricon media during printing. Theconductive wires 36, as previously noted, may be embedded in aconductive strip perpendicular to its length in order to make contact atone end with the electric paper 30 and at another end to a controllersuch as a circuit board (not shown). A problem with this design is thatthe conductive strip has no appreciable “memory” (rigidity) along itslength or width. Because of the supple nature of the conductive strip,direct contact between the conductive wires and the electric paper isnot consistent along the paper surface, therefore, the charging of thecharge-retention island 50 is inconsistent. The effects of thisinconsistency results in streaks and fringing of the printed images.

In view of these shortcomings, it has been realized that there is abenefit in incorporating a mechanism to provide the conductive stripwith an elastic character, i.e., resiliency, which will make theconductive strip compliant over uneven surfaces, while at the same timethe its original intended shape of the conductive strip.

Turning to FIG. 5, provided is an exploded partial view of a firstembodiment for a arrayed charge transfer device 68 a associated with theelectric reusable paper sheet 30 of the present application. Asillustrated, electric reusable paper sheet 30 may have an uneven surface70 (designated by the Δy, Δy′ and Δy″ designations). Charge transferdevice 68 a of the first embodiment, is comprised of the conductivestrip (Zebra connector) 32 with a flexible tapered arch spring support72. In this embodiment, spring support 72 may be at least one of metal,polymer or composites thereof. As illustrated in FIG. 5, a first orproximal end 72 a of spring support 72 is located nearest to theelectric paper sheet 30, and second or distal end 72 b is furthest fromelectric reusable paper sheet 30. Spring support 72 is formed in aflexible wedge design, wherein the thickness of the material increasesnearer the distal end 72 b. First or proximal end 72 a is alsoconsidered the leading edge of the conductive strip 32.

Turning to FIG. 6, in operation conductive strip 32 and spring support72 are held in place in a secure arrangement by clamp 76. As alsoillustrated in this figure, conductive strip 32 is in association with acircuit board 78, whereby power is selectively provided to individualconductive wires 36 of conductive strip 32. By this design, theconductive wires are selectively supplied with power to cause aselective activation/movement of bichrome balls 20 as charge isselectively applied to islands 50. The actual connections betweenconductive strip 32 and circuit board 78 are well known in the art andwill not, therefore, be discussed in greater detail.

With continuing attention to FIGS. 5 and 6, it may be noted thataddition of spring support 72 provides a progressive pressure onto thesurface of the charge-retaining islands 50. As the bending of conductivestrip 34 increases, stiffness caused by the increased material near thedistal end 72 b results in greater application of pressure onto thecharge-retaining island 50, insuring a reliable contact between theconductive wires 36 of conductive strip 34 and surface ofcharge-retaining islands 50.

The progressive pressure addresses the situation where the surface isuneven or debris/dirt is on the surface of electric reusable paper sheet30. Particularly, when an impediment, such as impediment 64 of FIG. 4,is encountered on the surface of the electric reusable paper sheet 30,progressive pressure will cause an increase pressure on the conductivestrip 32 in a quicker, more resilient manner such that as the conductivestrip moves past the impediment 64, more immediately and aggressivelymoves downward into contact with the next charge-retaining island 50.Use of spring support 72 also acts to restrict the first end or leadingedge 72 a of spring support 72 from curling upward when a downwardpressure is applied. These benefits are also obtained by use of thefollowing embodiments.

Dependant on the material of spring support 72, an optional pliableinsulator 80 may be appropriate. If, for example, spring support 72 hasconductive features, isolation between the spring support 72 andconductive strip 32 is desirable. Therefore, insulator 80 isincorporated to provide isolation between the two components. Whileinsulator 80 may be pliable, its addition would need to be taken intoaccount to determine the specific construction parameter spring support72, in order to ensure appropriate pressure. Insulator 80 may haveadhesive characteristics which act to hold the conductive strip 32 andspring support 72, and/or may also provide a cushion between thecomponents. Still further, insulator 80 may be a single layer ormultiple layers.

Turning to FIG. 7, set forth is a partial exploded view of a chargetransfer device 68 b in accordance with a second embodiment. In thisdesign, single flexible tapered arch spring support 72, is replaced witha flexible leaf spring arch support 82, which includes more than one,and preferably a plurality of progressively shorter flexibly archedstrips 82 a-82 c. Flexible arch support strips 82 a-82 c are shown inthis embodiment as having a substantially uniform thickness throughouttheir length. The strips are arranged for the longest strip 82 a to beclosest to the conductive strip 32.

As shown more particularly in FIG. 8, and similar to the arrangement ofFIG. 6, the flexible leaf spring arch support 82 is held with conductivestrip 32 by a clamp 76 on one side, which by the arrangement shownplaces conductive strip 32 in association with circuit board 78. Thisdesign, again, similar to FIG. 6, permits signals to be selectivelysupplied to conductive wires 36 to provide a charge to charge-retentionislands 50. As may be seen in the side view of FIG. 8, individualflexible leaf spring arch strips 82 a-82 c are arranged in aprogressively shorter (from the conductive strip 32) arrangement,provides an alternative design to obtain progressive pressure oncharge-retaining islands 50.

Similarly, as discussed in connection with FIGS. 5 and 6, thearrangement shown in the side view of FIG. 8 results in a progressivepressure which permits the conductive strip 32 to more aggressively moveback into contact with charge-retaining island 50 after the conductivestrip 32 has encountered an impediment.

Also similar to the previous embodiment, the optional pliable insulator80 may be incorporated when the arch strips 82 a-82 c have conductivecharacteristics.

Turning attention to FIG. 9, shown is a partial exploded view of acharge transfer device 68 c in accordance with a third embodiment. Inthis design, a flexible slitted arch strip 84 includes a plurality offingers 86 created by slits 88. Insulator 80 is positioned between theflexible slitted arch strip 84 and conductive strip 32. Flexible slittedarch strip 84 is a back structure to the conductive strip 32, allowingthe conductive strip to be compliant over the uneven surfaces andthereby provides reliable contact to the charge-retaining islands 50.Thus flexible slitted arch strip 84 is designed to provide theconductive strip 32 with the elastic character, i.e., resiliency itlacks. Flexible slitted arch strip 84, may be formed from metal, plasticor other composite. The fingers 86 formed by slits 88 having reliefholes 89 add to the flexibility provided as charge transfer device 68 cmoves over the surface of electric paper sheet 30. For example, when thesurface is uneven (or there is dirt/debris) in a particular area,fingers 86 directly over and close to that area will be lifted alongwith that portion of conductive strips 32, whereas the remaining fingers86 not near the uneven area will maintain downward pressure, keepingconductive strip 32 in contact with the surface. This provides a refinedadjustment for an individual area of the conductive strip. The side viewof FIG. 10 again shows the flexible slit arch strip 84 c, insulator 80and conductor strip 32 clamped by clamp 76, such that a connection tocircuit board 78 provides power selectively to the conductive wires 36of conductive strip 32.

It is to be appreciated that the first and second embodiments previouslydiscussed may incorporate the slitted features shown in the embodimentsof FIGS. 9 and 10. More specifically, the flexible arch spring support72 may incorporate not only the wedge-type feature providing progressivepressure, but may also be formed with the slitted features of FIGS. 9and 10. Such a design will then have the benefits of the progressivepressure and also the capability to provide a more refined movement overthose areas specifically affected by a impediment. A similar design mayalso be implemented in the embodiment shown by FIGS. 7 and 8. In thisdesign, the individual leaf strips 82 a-82 c are provided with the slitfeatures of FIGS. 9 and 10.

Turning to FIGS. 11 and 12, depicted is a further embodiment of a chargetransfer device 68 d incorporating a flexible curved channel 90 which isused as a back structure to conductive strip 32. Curved channel 90 isdesigned to provide conductive strip 32 with elastic characteristicsthat it otherwise would lack. Insulator 80 is used between conductivestrip 32 and curved channel 90. As in previous embodiments, insulator 80may be formed as an adhesive and/or cushion. As part of channel 90, arm90 a is raised at an angle whereby its upper edge 90 b, is positioned toreceive a cantilever beam 92. As depicted more clearly in FIG. 12,cantilever beam 92 is held by clamp 94 and is designed to provide adownward force on edge 90 a of curved channel 90, which in turn isapplied to conductive strip 32 and electric paper sheet 30. A straingauge arrangement 96, which may include a single strain gauge or aplurality of strain gauges, is connected to a bottom surface ofcantilever beam 92. The output of strain gauge arrangement 96 isprovided to a strain meter 98. Data from strain meter 98 is provided toa controller 100, on circuit board 78, via feedback line 102. Throughthis design, data can be processed to determine a desired contactpressure of the conductive strip 32. This contact pressure can then beused as the feedback to set a printhead contact pressure prior to eachprint cycle. Channel 90 and cantilever beam 92 may be made and formedfrom metal, plastic or other composite. For predictability purposes, thecantilever beam should be constructed from a predictable material, suchas copper or steel, with the characteristics of a spring.

Turning to FIG. 13, illustrated is a cross-sectional view of a furtherembodiment of the present application. In this design, conductive strip32 is shown in cross-section at one of conductive wires 36, shown asdotted line 36. In this particular embodiment, the non-conductivematerial 34 is depicted at the top, indicating conductive wire 36 doesnot extend from the top to bottom of conductive strip 32. However, inother embodiments electric wire 36 may extend the length of theconductive strip 32. In either case, as in previous embodiments, asecond component (i.e., support) 106 is placed in operational contactwith a first surface of conductive strip 32. The first component 104, asin the previous embodiment, is a support element and is intended torepresent each of the foregoing support element embodiments, includingthe spring support 72, multi-layered leaf spring support 82, the slittedsupport 84, conductive channel 90 and the further embodimentsincorporating elements of these.

In addition to this first component 104, a second component 106 is alsonow provided. In this design, second component 106 may also be any ofthe aforementioned embodiments discussed in connection with component104. Thus, conductive strip 32 has support elements on both sidesurfaces. This design permits for a bidirectional operation of thesystem across electric paper 30. Particularly, in one embodiment, inmoving in a first direction, the charge-transfer device 108 will more ina first direction generating an image, and then when reaching an end ofelectric paper 30, may move in a second direction back toward the firstlocation, erasing certain image elements. Alternatively, of course, thesystem may write in both directions or read in both directions. Thesystem will be held by the clamp mechanism, and will be supplied withsignals in accordance with the previously discussed processes.

It is to be appreciated that, while the foregoing description sets forthembodiments for charge transfer devices, the concepts of the presentapplication may be equally extended to other embodiments upon anunderstanding of the present application. Particularly, it is understoodothers will recognize modifications and adaptations of the illustratedembodiments which are in accord with the principles of the presentapplication. Therefore, the scope of the present application is to bedefined by the appended claims.

1. An electric display system comprising: an electric display materialhaving two opposing outer surfaces; and a charge transfer devicearranged in operative association with the display material, and havinga first component made of a pliable non-conductive material and at leastone conductive portion, and a second component configured to support thefirst component, wherein the second component provides an elasticcharacter to the first component, making it compliant over unevensurfaces while maintaining its original intended shape, the secondcomponent configured to become progressively stiffer as deflectionincreases.
 2. The display according to claim 1, wherein the secondcomponent provides an elastic character to the first component making itcompliant over uneven surfaces while maintaining its original intendedshape, the second component configured to become progressively stifferas deflection increases.
 3. The display according to claim 1, whereinthe second component is a flexible tapered spring arch support, which isthickest at a first end which is intended to be distant from thecharge-retaining islands.
 4. The display according to claim 1, whereinthe second component is a flexible leaf spring arch support including aplurality of progressively shorter arch strips positioned on top of eachother, with the longest of the arch strips nearest the first componentand the shortest of the arch strips farthest from the first component.5. The display system according to claim 1, further including aninsulating component located between the first component and the secondcomponent, the insulating component providing electrical isolationbetween the first and second components.
 6. The display system accordingto claim 5, wherein the insulating component includes adhesivecharacteristics, wherein the first component and second component areheld in place by the insulating component.
 7. The display systemaccording to claim 5, wherein the insulating component has a pliablecharacteristic which provides a cushion between the first component andthe second component, increasing compliance of the charge transferdevice.
 8. The display system according to claim 1, further including aclamp arranged to hold ends of the first component and the secondcomponent distant from the electric display material.
 9. The displaysystem according to claim 1, wherein the second component is a flexibletapered spring arch support, which is thickest at a first end which isintended to be distant from the electric display material.
 10. Thedisplay system according to claim 1, further including a thirdcomponent, wherein the second component supports the first component ona first side, and the third component is positioned to support the firstcomponent on a second side.
 11. The display system according to claim10, wherein the first component, second component and third componentare arranged for bi-directional operation of the charge transfer device.12. An electric display system comprising: an electric display materialhaving two opposing outer surfaces; and a charge transfer devicearranged in operative association with the display material, and havinga first component made of a flexible non-conductive material and aplurality of individually adjustable conductive elements, whereinmovement of one adjustable conductive element does not result inmovement of another adjustable conductive element.
 13. The electricdisplay according to claim 12, wherein the first component is a flexibleblock of material, and the individually adjustable elements are chargetransfer fingers, having at least a portion located within the flexibleblock of material.
 14. The electric display according to claim 13,wherein the charge transfer fingers include an end portion extendingfrom the flexible block at a direction towards the electric displaymaterial.
 15. The electric display according to claim 12, wherein theflexible non-conductive material includes a plurality of slits along alength of the material, defining individual flaps which are at one endfree to move independently of each other, and at a second end areinterconnected.
 16. The electric display according to claim 15, whereinthe adjustable conductive elements are flat pieces of metal extending ina length direction to form a plurality of adjustable flat fingers whichare free to move at a first end.
 17. The display system according toclaim 12, wherein the charge transfer device is configured to operatebi-directionally.
 18. The display according to claim 12, furtherincluding a second component, wherein the second component provides anelastic character to the first component making it compliant over unevensurfaces while maintaining its original intended shape, the secondcomponent configured to become progressively stiffer as deflectionincreases.
 19. The display system according to claim 18, furtherincluding an insulating component located between the first componentand the second component, the insulating component providing electricalisolation between the first and second components.
 20. The displaysystem according to claim 19, further including a third component,wherein the second component supports the first component on a firstside, and the third component is positioned to support the firstcomponent on a second side.